Adding extra field input

I am slowly developing a database to store the names of songs and their songwriters.

Some songs have 1 writer, others have more than 1.

On the input tableI would like to have a single entry field for "writer" with an "add another writer" button that brings up another entry box, where the data goes to the same field (as I am basing a value list around this field).

I know that I can achieve something similar with field repetitions, or having multiple fields, but I think that both of those solutions look awkward.